An international team of researchers proposes to examine the development of face processing from infancy through adolescence. We will investigate how infants' and children's face processing expertise is tuned by their experience with different classes of faces early in development. Children from infancy through adolescence and from different countries will be tested to determine how their experience with faces of different race, gender, age, and species affect their ability to classify faces into different categories and to recognize the identity of individual faces. We will test the hypothesis that while the human visual system may be biased at birth to favor face-like stimuli, much of our face processing ability is acquired through experience with thousands of faces over the course of development. Differential degrees of exposure to different categories of faces (race, gender, age, and species) will impact on how humans classify faces into different face categories and how they recognize individual faces within these general categories. Analogous to phonetic development, at early stages of face expertise acquisition, infants and children may process a broad range of faces from different races, genders, ages, and species with equal facility. As children mature and are selectively exposed to a limited number of face categories (one's own species, race, gender, and age group), their face expertise becomes more specialized. As they become increasingly more skilled at processing faces with which they have extensive experience (expertise), they lose their natural ability to process faces from face categories with which they have limited experience. This research program will provide much needed information to form a comprehensive picture of the development of face processing abilities and to delineate the role of experience in the formation of face expertise. Our research should facilitate the development of a general theory of face processing in children and adults. The methods we refine for this project should be of use for clinical studies and assessments that involve children with atypical trajectories in the development of face processing including cases of autism and developmental prosopagnosia.